A standard multiple bolt door latch has a main bolt that is spring loaded and that is received in a keeper at knob-level in the door jamb and one or more secondary bolts that engage in the door frame at other locations, typically in the lintel and sill. An actuating lever can be displaced in one direction, normally downward, to retract all the bolts and oppositely to extend the secondary bolts. The spring-loaded main bolt always projects from the door but can be deflected inward to hold it shut without actuation of the lever.
The advantage of this system is that for low-security latching of the door it is merely necessary to close it so that it is caught by the spring-loaded main bolt, and it can be opened easily by simply moving the lever down into its lower end position to retract this main bolt. For positive multipoint locking the lever is pulled up into its upper end position to extend the secondary bolt or bolts. The same downward actuation that retracts the main bolt will also, if necessary, retract the secondary bolt or bolts.
The main disadvantage is that if the handle is moved up when the door is open, the secondary bolts are extended. When the door is then closed, they can damage the door frame and scrape on the floor.